Dirty Hydrogen Cars
Today's Wall St. Journal contains an excellent article highlighting findings of a soon-to-be released study by the Argonne National Laboratory on the effects of running an internal combustion engine car on hydrogen. Apparently the study will support earlier work by a number of researchers indicating that, unless the hydrogen in question is produced entirely from renewable sources, such as wind or solar power, the net result for the environment is no better than burning reformulated gasoline in an ordinary--and much less expensive--car.
BMW has been pushing its hydrogen-powered, internal combustion 7-Series for several years. This should come as no surprise, since the original technology to do this was developed in Germany in the 1930s.
The problem with this approach is stunningly simple: when you add the emissions from making hydrogen from natural gas--the way 99% of all hydrogen today is generated--to the emissions from burning it in an engine, the result is essentially the same as for a conventional car. This kind of analysis is called "well-to-wheels", and it is a much superior way of assessing total environmental impact than the traditional approach of simply measuring what comes out of a car's tailpipe.
In fact, even supplying hydrogen from renewable sources would not improve the picture very much for cars like the BMW 745H, since the electricity produced by the windmills or solar panels might be better employed backing down much dirtier generators, such as coal-fired power plants. This sounds like confusing and circular logic, but it reflects the reality that today's energy networks are highly inter-related.
This is why other manufacturers, such as General Motors, are eschewing the route BMW has chosen and concentrating on fuel cells. Although the same logic chain of "well-to-wheels" is equally applicable to fuel cells, they win in a number of areas. First, vehicles powered by fuel cells would truly have zero tailpipe emissions, unlike hydrogen powered internal combustion cars. In addition, their efficiency is inherently 2-3 times greater, so that the amount of hydrogen they will consume per mile is much less, and thus the amount of natural gas used--with its associated emissions--is much less.
Even if fuel cells never become economically viable, the true standard of comparison for a hydrogen-powered car should not be a conventional car, but the hybrid cars that are already available, such as the Toyota Prius, with many more hybrid models due on the market in the next two years. Hybrids are cleaner than conventional vehicles, from both a tailpipe and "well-to-wheels" standpoint, and they create a competitive bar that no hydrogen-powered internal combustion engine car can match.
The bottom line is that it is expensive to produce hydrogen and difficult to store it and use it on board a car. It only makes sense to go to these lengths if the hydrogen can be used in the car in a way that truly improves both the environment and our energy balance.